Methods and systems for planarizing microelectronic devices with Ge-Se-Ag layers

ABSTRACT

Microelectronic devices including a layer of germanium and selenium, optionally including up to 10 atomic percent silver, show promise for select applications. Manufacturing microelectronic devices containing such layers using conventional CMP processes presents some significant challenges. Embodiments of the invention provide methods of planarizing workpieces with Ge—Se layers, many of which can be carried out using conventional CMP equipment. Other embodiments of the invention provide chemical-mechanical polishing systems adapted to produce planarized workpieces with Ge—Se layers or, in at least one embodiment, other alternative layers. Various approaches suggested herein facilitate production of such microelectronic devices by appropriate control of the down force of the Ge—Se layer against the planarizing medium and/or one or more aspects of the planarizing medium, which aspects include pH, abrasive particle size, abrasive particle hardness, weight percent of abrasive.

TECHNICAL FIELD

The present invention provides certain improvements in processingmicroelectronic devices. The invention has particular utility inconnection with planarizing microelectronic devices with Ge—Se—Aglayers.

BACKGROUND

Mechanical and chemical-mechanical planarizing processes (collectively“CMP”) remove material from the surface of semiconductor wafers, fieldemission displays or other microelectronic workpieces in the productionof microelectronic devices and other products. FIG. 1 schematicallyillustrates a CMP machine 10 with a platen 20, a carrier assembly 30,and a planarizing pad 40. The CMP machine 10 may also have an under-pad25 attached to an upper surface 22 of the platen 20 and the lowersurface of the planarizing pad 40. A drive assembly 26 rotates theplaten 20 (indicated by arrow F), or it reciprocates the platen 20 backand forth (indicated by arrow G). Since the planarizing pad 40 isattached to the under-pad 25, the planarizing pad 40 moves with theplaten 20 during planarization.

The carrier assembly 30 has a head 32 to which a microelectronicworkpiece 12 may be attached, or the microelectronic workpiece 12 may beattached to a resilient pad 34 in the head 32. The head 32 may be afree-floating wafer carrier, or an actuator assembly 36 may be coupledto the head 32 to impart axial and/or rotational motion to the workpiece12 (indicated by arrows H and 1, respectively).

The planarizing pad 40 and a planarizing solution 44 on the pad 40collectively define a planarizing medium that mechanically and/orchemically removes material from the surface of the workpiece 12. Theplanarizing pad 40 can be a soft pad or a hard pad. The planarizing pad40 can also be a fixed-abrasive planarizing pad in which abrasiveparticles are fixedly bonded to a suspension material. In fixed-abrasiveapplications, the planarizing solution 44 is typically a non-abrasive“clean solution” without abrasive particles. In other applications, theplanarizing pad 40 can be a non-abrasive pad composed of a polymericmaterial (e.g., polyurethane), resin, felt or other suitable materials.The planarizing solutions 44 used with the non-abrasive planarizing padsare typically abrasive slurries with abrasive particles suspended in aliquid. The planarizing solution may be replenished from a planarizingsolution supply 46.

If chemical-mechanical planarization (as opposed to plain mechanicalplanarization) is employed, the planarizing solution 44 will typicallychemically interact with the surface of the workpiece 12 to speed up orotherwise optimize the removal of material from the surface of theworkpiece. Increasingly, microelectronic device circuitry (i.e.,trenches, vias, and the like) is being formed from copper. Whenplanarizing a copper layer using CMP, the planarizing solution 44 istypically neutral to acidic and includes an oxidizer (e.g., hydrogenperoxide) to oxidize the copper and increase the copper removal rate.One particular slurry useful for polishing a copper layer is disclosedin International Publication Number WO 02/18099, the entirety of whichis incorporated herein by reference.

To planarize the workpiece 12 with the CMP machine 10, the carrierassembly 30 presses the workpiece 12 face-downward against the polishingmedium. More specifically, the carrier assembly 30 generally presses theworkpiece 12 against the planarizing solution 44 on a planarizingsurface 42 of the planarizing pad 40, and the platen 20 and/or thecarrier assembly 30 move to rub the workpiece 12 against the planarizingsurface 42. As the workpiece 12 rubs against the planarizing surface 42,material is removed from the face of the workpiece 12.

CMP processes should consistently and accurately produce a uniformlyplanar surface on the workpiece to enable precise fabrication ofcircuits and photo-patterns. During the construction of transistors,contacts, interconnects and other features, many workpieces developlarge “step heights” that create highly topographic surfaces. Suchhighly topographical surfaces can impair the accuracy of subsequentphotolithographic procedures and other processes that are necessary forforming sub-micron features. For example, it is difficult to accuratelyfocus photo patterns to meet tolerances approaching 0.1 micron ontopographic surfaces because sub-micron photolithographic equipmentgenerally has a very limited depth of field. Thus, CMP processes areoften used to transform a topographical surface into a highly uniform,planar surface at various stages of manufacturing microelectronicdevices on a workpiece.

Chalcogenide materials can be used as electrically writable and erasablephase change materials, i.e., they can be electrically switched betweengenerally amorphous and generally crystalline states with differentresistive properties, or between different resistive states while incrystalline form. Such electrically writable and erasable materials areuseful in a number of applications, including non-volatile or“state-changeable” memory devices such as EEPROMs and FLASH memorydevices. Chalcogenide alloys have also garnered much attention aspossible elements of optical memory devices. Certain aspects ofmanufacturing devices including chalcogenide materials are disclosed inU.S. Pat. No. 5,789,277 (Zahorik et al.), the entirety of which isincorporated herein by reference. Germanium-tellurium (Ge—Te) andgermanium-tellurium-antimony (Ge—Te—Sb) are, perhaps, the most commonchalcogenide-metal alloys in current EEPROM and Flash applications.Increasingly, though, memory device manufacturers are investigatingother chalcogenides as possible candidates for both electricallywritable and erasable materials and optical memory applications.

SUMMARY

Various embodiments of the present dimension provide methods ofplanarizing workpieces with germanium-selenium layers orchemical-mechanical polishing systems adapted to produce planarizedworkpieces, e.g., workpieces with germanium-selenium layers. Oneexemplary embodiment provides a method of planarizing a microelectronicworkpiece which includes a substrate having a surface, an outer layerdefining a polished face of the workpiece, and an intermediate layerdisposed between the substrate surface and the outer layer. This outerlayer may comprise (Ge_(x)Se_(y))_(a)Ag_(b), wherein x is about 20-80, yis about 20-80, a is about 90-100, and b is about 0-10. In accordancewith this method, a planarizing solution is delivered to a planarizingsurface of the planarizing pad. The planarizing solution and theplanarizing pad together comprise a planarizing medium. The planarizingsolution has a pH of at least 7; in one embodiment, the pH is greaterthan 7. The planarizing medium includes abrasive articles having a meanparticle size of no greater than about 100 nm. Material of the outerlayer is removed by pressing the unpolished face of the workpieceagainst the polishing medium with a down force of no greater than about4 psi. One useful application employs a down force of no greater thanabout 2 psi.

In one more specific adaptation of this embodiment, the planarizingsolution includes a fluid component having a pH of about 8-11.5. Theplanarizing medium includes an abrasive comprising abrasive particleshaving a mean particle size of about 30-100 nm and a Vickers hardnessnumber of less than about 1500. Material of the outer layer is removedby pressing the unpolished face of the workpiece against the polishingmedium with a down force of at least about 0.1 psi and no more thanabout 2 psi.

One alternative embodiment provides a method of planarizing amicroelectronic workpiece which includes a substrate and an outer layercomprising germanium and selenium. The outer layer optionally includessilver, as well. The microelectronic workpiece is loaded into a carrierassembly of a CMP machine. A planarizing solution is delivered to aplanarizing pad. The planarizing solution and planarizing pad comprise aplanarizing medium. The planarizing solution includes a fluid componenthaving a pH of about 8-11.5 and a solid component comprising abrasiveparticles. Material of the outer layer is removed from the workpiece byrubbing the outer layer against the planarizing medium with a controlledforce. In one embodiment, the material of the outer layer is removed byrubbing without substantial delamination of the outer layer. In anotherembodiment, the controlled force is about 0.1-2 psi.

A different embodiment of the invention provides a chemical-mechanicalpolishing system. This system may include a carrier assembly includingan actuator, a planarizing medium, a workpiece, and a controlleroperatively coupled to the actuator. The planarizing medium, which maycomprise a planarizing solution and a planarizing pad, includes anabrasive comprising abrasive particles having a mean particle size ofabout 30-100 nm and a Vickers hardness number of less than about 1500.The planarizing solution may comprise a fluid component having a pH ofat least about 7, and preferably at least about 8, e.g., about 8-11.5.The workpiece, which is loaded into the carrier assembly, has an outerlayer comprising germanium and selenium which is oriented toward theplanarizing medium. The controller controls the actuator to control adown force of the outer layer against the polishing medium to a range ofabout 0.1-2 psi.

Still another embodiment provides an alternative chemical-mechanicalpolishing system that is well suited for use with a Ge—Se layer, but maybe used to planarize other films, too. This system includes a carrierassembly including an actuator. The carrier assembly is adapted to holdthe workpiece with an outer layer facing downwardly. A planarizingmedium comprises a planarizing solution and a planarizing pad. Theplanarizing medium includes an abrasive comprising abrasive particleshaving a mean particle size of about 30-100 nm and a Vickers hardnessnumber of less than about 1500. The planarizing solution comprises afluid component having a pH of about 7-11.5, e.g., about 8-11.5. Acontroller, which may be operatively coupled to the actuator, controlsthe actuator to control a down force of the outer layer of the workpieceagainst the polishing medium to a range of about 0.1-2 psi.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a planarizing machine inaccordance with the prior art.

FIG. 2 is a schematic cross-sectional view of a portion of amicroelectronic workpiece.

FIG. 3 is a schematic illustration of a stage in the planarization ofthe microelectronic workpiece shown in FIG. 2.

FIG. 4 is a schematic cross-sectional view of the microelectronicworkpiece shown in FIG. 2 after planarization.

DETAILED DESCRIPTION

Various embodiments of the present invention provide methods andapparatus for processing microelectronic devices with Ge—Se—Ag layers.The following description provides specific details of certainembodiments of the invention illustrated in the drawings to provide athorough understanding of those embodiments. It should be recognized,however, that the present invention can be reflected in additionalembodiments and the invention may be practiced without some of thedetails in the following description.

The owner of the present invention is investigating thin films orstructures comprising germanium and selenium, or germanium, selenium,and silver (collectively referred to below as Ge—Se—Ag chalcogenides orGe—Se—Ag films, even though some of these films may not include anysilver) in forming functional elements of select microelectronicdevices, e.g., in non-volatile memory applications. Materials currentlycontemplated for such applications have the general formula(Ge_(x)Se_(y))_(a)Ag_(b), wherein x is about 20-80, y is about 20-80, ais about 90-100, and b is about 0-10. It should be appreciated, however,that in some embodiments the values of x, y, a, and b are not limited tothese ranges.

FIG. 2 schematically illustrates one possible structure of amicroelectronic workpiece 50 employing a Ge—Se—Ag film. In thisembodiment, the microelectronic workpiece 50 includes a substrate 52having at least one recess 54 formed therein. The structure can behelpful in forming specific Ge—Se—Ag structures, e.g., conductive linesor vias of electronic circuitry, or electrically isolated lines, rings,or serpentine structures.

A Ge—Se—Ag film may comprise an outer layer 70 of the workpiece 50. Thisouter layer 70 may substantially fill the recess 54 and extend over theentire outer surface 56 of the substrate 52, or at least a workingportion of the substrate 52. The Ge—Se—Ag chalcogenide may be depositedin any suitable fashion, e.g., using electrolytic deposition, chemicalvapor deposition (CVD), physical vapor deposition (PVD), or atomic layerdeposition (ALD). At this stage, the outer layer 70 is contiguous acrossthe outer surface 56 of the substrate. If specific shapes or islands ofGe—Se—Ag chalcogenide are to be formed, an overburden of the outer layer70 extending outwardly beyond the upper edge of the recess 54 will beremoved, leaving the Ge—Se—Ag chalcogenide only in the filled recesses54. In other embodiments, it may be desirable to form a thin,monolithic, contiguous Ge—Se—Ag film. However, the outer, unpolishedface 72 of the outer layer 70 may have an irregular, topographicsurface. As noted above, such topographic surfaces may be unsuitable forfurther processing steps, e.g., photolithographic procedures, and it maybe advisable to planarize this surface before such further processing.

In the structure illustrated in FIG. 2, the microelectronic workpiece 50includes an intermediate layer 60 disposed between the outer surface 56of the substrate 52 and the outer layer 70. In the illustratedembodiment, the intermediate layer 60 extends over the entire outersurface 56 of the substrate 52, including the interior surface of therecess 54. In other embodiments, the intermediate layer 60 may beapplied before the recess 54 is formed and the interior surface of therecess 54 will not include the intermediate layer 60. Such anintermediate layer 60 can be used for a variety of purposes. Forexample, the intermediate layer 60 may function as a diffusion barrier,limiting diffusion of the material of the outer layer 70 into thesubstrate 52 and vice versa. In other embodiments, the intermediatelayer 60 may function merely as a polish stop, as discussed in moredetail below. The composition and thickness of the intermediate layer 60will depend on a number of factors, including the function of theintermediate layer (e.g., as a diffusion barrier or as a polish stop).Suitable materials for the intermediate layer 60 include tungsten,tantalum, platinum, silica, and silicon nitride. An intermediate layercomprising silicon nitride has functioned effectively as a polish stoplayer, as described below.

CMP is commonly employed to planarize microelectronic workpieces havinglayers of copper or aluminum at commercially useful throughputs. Asnoted above, copper CMP operations typically employ neutral to acidicsolutions. For example, International Publication Number WO 02/18099(incorporated by reference above) suggests a copper planarizing slurryhaving a pH of about 2-6.

Ge—Se—Ag films, however, cannot be effectively and safely manufacturedunder such conditions. The presence of selenium in the Ge—Se—Ag filmspresents some chemical handling difficulties, in part because seleniumhydride is highly toxic. Planarizing Ge—Se—Ag films can generateselenium hydride as a toxic fume. If selenium is allowed to oxidize, theoxide is more readily converted to the hydride, increasing the risk ofproducing a toxic gas during planarization. When manufacturing limitedquantities of microelectronic devices employing Ge—Se chalcogenides forresearch purposes, these films can be planarized in a highly ventilatedarea, such as a hood. This is not practical in mass production on acommercial scale using conventional CMP apparatus and techniques.Although a basic solution can help limit the generation of toxicbyproducts, it has been discovered that Ge—Se—Ag films can also dissolvein strongly basic solutions, which may make it difficult to control thepolishing rate.

Silver also tends to be relatively mobile in Ge—Se—Ag films. Under CMPconditions commonly employed in planarizing copper films, for example,silver may tend to come out of solution and migrate to the surfaceduring planarization and agglomerate on the surface. This leads to filmswith non-homogenous compositions and surface characteristics that varyfrom one location to another across the workpiece.

Another concern in planarizing Ge—Se—Ag films is that such films maydelaminate from the workpiece during a planarizing cycle. In someapplications, Ge—Se—Ag films may be applied over a layer of tungsten,tantalum, platinum, silica, or silicon nitride. Unfortunately, adhesionof these Ge—Se—Ag films to such underlayers is relatively poor.Conventional CMP processing techniques and conditions could causeGe—Se—Ag films to delaminate from the underlying substrate, leading tofaulty electrical connections and defective products.

It also can be difficult to predict and carefully control the polishrate of Ge—Se—Ag films, i.e., the rate at which the films are removed.This is due, at least in part, to significant variations of the polishrate with relatively small changes in the composition of the Ge—Se—Agfilms. In some commercial CMP operations, the workpiece is planarizedfor a fixed period of time. If the polishing rate of a Ge—Se—Ag filmvaries from one workpiece to the next, planarizing for a fixed period oftime could lead to appreciable variations in the thickness of the filmremoved during the planarization.

Some embodiments of the invention address some or all of thesedifficulties to provide a practical, commercially viable process forplanarizing Ge—Se—Ag films. In particular, smooth, planarized surfacescan be produced without substantial delamination or silver agglomerationby appropriately controlling aspects of the pH, controlling abrasivematerial in the planarizing medium, and/or limiting the down forceagainst the Ge—Se—Ag film.

As noted above, FIG. 1 illustrates a conventional CMP machine.Embodiments of the invention can be carried out on such a conventionalCMP machine. In such embodiments, a microelectronic workpiece having aGe—Se—Ag film, e.g., the microelectronic workpiece 50 of FIG. 2, isloaded in the carrier assembly 30 of the CMP machine 10, e.g., byattaching the workpiece 50 to the resilient pad 34 of the head 32. Theactuator assembly 36 then lowers the head 32 to juxtapose the outersurface 72 of the outer layer 70 (FIG. 2) with the planarizing medium,i.e., the planarizing pad 40 and the liquid planarizing solution 44.

The actuator assembly 36 may also rotate the workpiece 50 and pushes theworkpiece 50 against the planarizing medium with a controlled,predetermined down force during the course of the planarizing operation.The actuator assembly may include a controller 37, e.g., a programmedprocessor, which controls operation of the actuator assembly, includingthe rotational velocity of the workpiece 50 with respect to theplanarizing medium and the down force. Rotating the workpiece 50 at arelative velocity of about 10-100 in. per second should be appropriate,though other rotational speeds may also work. In one embodiment, thedown force is relatively low to reduce the likelihood of delaminatingthe Ge—Se—Ag film from the underlying intermediate layer 60 or substratesurface 56. For certain applications, a down force of no more than about2 psi is appropriate. In other applications, the down force should beabout 0.1-1.9 psi.

The planarizing solution 44 can be delivered from the planarizingsolution supply to the planarizing surface 42 of the planarizing padduring the course of planarizing the workpiece. To avoid generatingtoxic byproducts from the selenium in the Ge—Se—Ag film, the planarizingsolution may be basic. Depending on the stoichiometry of the film andother factors, the planarizing solution may range from a mild base to afairly strong base. For most applications, it is expected that a pH fromabout 7 to about 11.5 will work well. For example, a pH level of about 8to about 11.5 is expected to be useful in many applications. Lower pHlevels than this will increase the risk of creating toxic byproductsfrom the selenium. On the other hand, as the pH level increases abovethis range, it has been found that Ge—Se—Ag chalcogenides becomeincreasingly soluble in the planarizing solution, adversely affectingthe integrity of the Ge—Se—Ag film. For films having more silver (e.g.,8-10 atomic % or greater), a planarizing solution with a pH over 11.5may be employed. For Ge—Se—Ag films with relatively little or no silver(e.g., 0-2 atomic %), planarizing solutions advantageously may have a pHin a lower portion of the stated range, e.g., about 7-10 or about 8-10,though a higher pH may also suffice. In one embodiment, the planarizingsolution comprises a base (e.g., potassium hydroxide or tetramethylammonium hydroxide) and deionized water in proportions selected to yieldthe desired pH. While an acidic buffer may be employed to help stabilizepH, planarizing solutions in some embodiments are substantially acid-feeto reduce the chance of generating toxic byproducts from the selenium inthe Ge—Se—Ag chalcogenide material.

In other embodiments, the planarizing solution includes ammonia. It isbelieved that the presence of the ammonia will reduce the rate ofselenium hydride production. In one specific formulation, theplanarizing solution comprises a combination of potassium hydroxide andammonia.

As noted above, the planarizing medium of the CMP machine typicallyincludes an abrasive. Fixed-abrasive CMP machines employ a planarizingpad 40 that has abrasive particles imbedded therein. Such fixed-abrasivepads may be a conventional round rotary pad, a web-format pad that canbe moved periodically to present a “fresh” abrasive area, or a belt,which is essentially a web-format pad arranged as a continuous loop. Inother embodiments, a non-abrasive planarizing pad (e.g., a urethanehaving a Shore D hardness of about 40-60, commercially available fromRodel as model WWP 3000) is employed and the abrasive particles areincluded in the planarizing solution 44.

Some abrasives used in conventional CMP operations may be too hard forpolishing Ge—Se—Ag films. For example, use of high-purity alumina, whichhas a Vickers hardness number of 1500 or more, increases the rate atwhich the outer layer 70 is removed, which could increase throughput. Ithas been found, however, that such hard abrasives can promotedelamination of the Ge—Se—Ag film from the underlying substrate 52 orintermediate layer 60, e.g., by separating the outer layer 70 from theintermediate layer at the interface 62 therebetween. In certainembodiments of the invention, therefore, the abrasive particles areformed of a material having a Vickers hardness of less than about 1500.Silica particles (which typically have Vickers hardness numbers on theorder of 1100 or less) have been found to work well and it isanticipated that ceria particles or mixtures of silica and ceriaparticles may also suffice.

It has also been found that abrasives with larger particle sizes canincrease the likelihood of delamination and agglomeration of silver atthe surface of the planarized Ge—Se—Ag film. Abrasive particles having amean particle size of less than about 100 nm are expected to suffice. Inone specific application, the mean particle size is about 30-100 nm. Inanother embodiment, a mean particle size of about 30-50 nm is employed.In one specific system found to work well, silica particles having amean particle size of about 50 nm were employed. The size distributionof the abrasive particles may be relatively narrow to avoid too manyoversized particles.

As noted above, the planarizing solution 44 may provide the abrasiveparticles used in the planarizing medium. Such a planarizing solutionwill have a fluid fraction, which may have a pH of about 7 to about11.5, and a solid fraction comprising the abrasive particles. Forexample, a pH level of about 8 to about 11.5 is expected to be useful inmany applications. Planarizing solutions in which the solid fraction isabout 1-30 weight percent are expected to work well. While higher weightpercentages of abrasive particles may be functional, this could increasethe chances of delamination and/or silver agglomeration.

FIG. 3 schematically illustrates a stage in the process of planarizingthe microelectronic workpiece 50 shown in FIG. 2. At this stage, theouter layer 70 of the partially polished workpiece 150 has a polishedface 74 which is juxtaposed with the planarizing face 42 of theplanarizing pad 40. The planarizing solution 44 is disposed between thepolished face 74 of the outer layer and the planarizing face 42 of theplanarizing pad 40. The intermediate layer 60 remains beneath thepolished face 74 of the outer layer 70 at this stage in the planarizingprocess.

FIG. 4 schematically illustrates a final planarized microelectronicworkpiece 250. At this stage, the entire overburden of the Ge—Se—Agouter layer 70 is removed, exposing a portion of the intermediate layer60. In the illustrated embodiment, a portion of the intermediate layer60 in the recess 54 of the substrate 52 remains covered by the remainderof the outer layer 70. In one embodiment of the invention, theintermediate layer 60 serves as a polish stop, helping automaticallydetect the end point of the planarizing process. In such an embodiment,the intermediate layer has a removal rate under the planarizingconditions of the CMP machine 10 that is slower than the removal rate ofthe Ge—Se—Ag film 70. This can be accomplished by employing a materialthat is less subject to chemical attack by the basic planarizingsolution 44 than is the Ge—Se—Ag film 70 and/or which is harder than theGe—Se—Ag film. In one particular application, the intermediate layer 60may comprise silicon nitride, which is both harder and more resistant tochemical attack than the adjacent Ge—Se—Ag film 70. Once the overburdenof the outer layer 70 is removed and the polishing medium begins to acton the intermediate layer 60, the friction between the polishing mediumand the workpiece 50 will change. As a consequence, the force necessaryto drive the polishing pad at a constant speed will change. This willcause a change in power to the drive assembly 26, which can be detectedas an indication that the polishing is complete. If the actuatorassembly 36 includes a controller 37, as noted above, the controller 37could be programmed to detect this change in friction and either set aflag signifying that polishing is complete or stop rubbing of theworkpiece 50 against the polishing medium.

Alternatively, the end point of the polishing process may be determinedoptically. Light reflected by the Ge—Se—Ag film 70 may differ in colorand/or intensity from the light reflected by the intermediate layer 60from the same light source. A controller 37 may be coupled to an opticalsensor in a known manner to detect the change in reflectance and eitherset an endpoint flag or stop polishing the workpiece 50.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from thespirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. A method of controlled material removal from a microelectronicworkpiece which includes a substrate having a surface, an outer layerdefining an unpolished face of the workpiece, and an intermediate layerdisposed between the substrate surface and the outer layer, the outerlayer comprising (GexSey)aAgb, wherein x is about 20-80, y is about20-80, a is about 90-100, and b is about 0-10, the method comprising:delivering a process solution to a process surface of a processing pad,the process solution and the processing pad comprising a removal medium,the process solution comprising a fluid component having a pH of about8-11.5, the removal medium including an abrasive comprising abrasiveparticles having a mean particle size of about 30-100 nm and a Vickershardness number of less than about 1500; and removing material of theouter layer by pressing the unpolished face of the workpiece against thepolishing medium with a down force of at least about 0.1 psi and no morethan about 2 psi.
 2. The method of claim 1 wherein the abrasive isdelivered to the processing pad as a solid component of the processsolution, the solid component comprising about 1-30 weight percent ofthe process solution.
 3. The method of claim 1 wherein the abrasive isdelivered to the processing pad as a solid component of the processsolution, the abrasive having a mean particle size of about 30-50 nm. 4.The method of claim 3 wherein the solid component comprises about 1-30weight percent of the process solution.
 5. The method of claim 1 whereinthe abrasive particles comprise silica or ceria particles.
 6. The methodof claim 5 wherein the abrasive particles comprise silica and ceriaparticles.
 7. The method of claim 1 wherein the fluid component of theprocess solution comprises at least one of potassium hydroxide andtetramethyl ammonium hydroxide.
 8. The method of claim 1 wherein theintermediate layer comprises a material having a hardness greater than ahardness of the outer layer, wherein the intermediate layer acts as apolish stop.
 9. The method of claim 1 wherein the intermediate layercomprises a material having a removal rate slower than a removal rate ofthe outer layer at the same down force in contact with the same removalmedium, wherein the intermediate layer acts as a polish stop.
 10. Themethod of claim 1 wherein the abrasive particles, the down force and apolishing linear velocity are selected to remove the material of theouter layer without substantial delamination of the outer layer from theintermediate layer or the substrate.
 11. A method of controlled materialremoval from a microelectronic workpiece which includes a substratehaving a surface, an outer layer defining an unpolished face of theworkpiece, and an intermediate layer disposed between the substratesurface and the outer layer, the outer layer comprising (GexSey)aAgb,wherein x is about 20-80, y is about 20-80, a is about 90-100, and b isabout 0-10, the method comprising: delivering a process solution to aprocess surface of a processing pad, the process solution and theprocessing pad comprising a removal medium, the process solution havinga pH greater than 7, the removal medium including abrasive particleshaving a mean particle size of no greater than about 100 nm; andremoving material of the outer layer by pressing the unpolished face ofthe workpiece against the polishing medium with a down force of nogreater than about 2 psi.
 12. The method of claim 11 wherein theabrasive particles, the down force and a polishing linear velocity areselected to remove the material of the outer layer without substantialdelamination of the outer layer from the intermediate layer or thesubstrate.
 13. The method of claim 11 wherein the abrasive particles,the down force and a polishing linear velocity are selected to removethe material of the outer layer without substantial agglomeration ofsilver on a polished surface of the outer layer.
 14. A method ofremoving material from a microelectronic workpiece, comprising: loadingthe microelectronic workpiece into a carrier assembly of a CMP machine,the microelectronic workpiece comprising a substrate including an outerlayer comprising germanium and selenium; delivering a process solutionto a processing pad, the process solution and processing pad comprisinga removal medium, the process solution comprising a fluid componenthaving a pH of about 8-11.5 and a solid component comprising abrasiveparticles; removing material of the outer layer from the workpiece byrubbing the outer layer against the removal medium with a controlledforce.
 15. The method of claim 14 wherein the material of the outerlayer is removed by rubbing without substantial delamination of theouter layer.
 16. The method of claim 14 wherein the solid componentcomprises about 1-30 weight percent of the process solution delivered tothe processing pad.
 17. The method of claim 14 wherein the abrasiveparticles of the process solution delivered to the processing pad have amean particle size of about 30-50 nm.
 18. The method of claim 17 whereinthe solid component comprises about 1-30 weight percent of the processsolution.
 19. The method of claim 14 wherein the abrasive particlescomprise silica or ceria particles.
 20. The method of claim 14 whereinthe controlled force is no greater than 2 psi.
 21. The method of claim14 wherein the controlled force is about 0.1-2 psi.
 22. The method ofclaim 14 wherein the microelectronic workpiece includes an intermediatelayer disposed between the substrate and the outer layer, outer layerbeing removed to expose the intermediate layer.
 23. The method of claim22 wherein the intermediate layer comprises a material having a removalrate slower than a removal rate of the outer layer, the intermediatelayer acting as a polish stop.
 24. The method of claim 14 wherein theouter layer includes up to 10 atomic percent silver, and the abrasiveparticles, the controlled force and a polishing linear velocity areselected to remove the material of the outer layer without substantialagglomeration of silver on a polished surface of the outer layer.
 25. Amethod of removing material from a microelectronic workpiece,comprising: loading the microelectronic workpiece into a carrierassembly of a CMP machine, the microelectronic workpiece comprising asubstrate including an outer layer comprising germanium and selenium;delivering a process solution to a processing pad, the process solutionand processing pad comprising a removal medium, the process solutioncomprising a fluid component having a pH of at least about 8 and a solidcomponent comprising abrasive particles having a particle size of about30-100 nm; removing material of the outer layer from the workpiece byrubbing the outer layer against the removal medium with a controlledforce.
 26. The method of claim 25 wherein the material of the outerlayer is removed by rubbing without substantial delamination of theouter layer.
 27. The method of claim 25 wherein the solid componentcomprises about 1-30 weight percent of the process solution delivered tothe processing pad.
 28. The method of claim 25 wherein the abrasiveparticles of the process solution delivered to the processing pad have amean particle size of about 30-50 nm.
 29. The method of claim 25 whereinthe abrasive particles comprise silica or ceria particles.
 30. Themethod of claim 25 wherein the fluid component has a pH no greater thanabout 11.5.
 31. The method of claim 25 wherein the controlled force isno greater than 2 psi.
 32. The method of claim 25 wherein themicroelectronic workpiece includes an intermediate layer disposedbetween the substrate and the outer layer, the outer layer being removedto expose the intermediate layer.
 33. The method of claim 30 wherein theintermediate layer comprises a material having a removal rate slowerthan a removal rate of the outer layer, the intermediate layer acting asa polish stop.
 34. The method of claim 25 wherein the outer layerincludes up to 10 atomic percent silver, and the abrasive particles, thecontrolled force and a polishing linear velocity are selected to removethe material of the outer layer without substantial agglomeration ofsilver on a polished surface of the outer layer.
 35. A method ofcontrolled material removal from a microelectronic workpiece,comprising: loading the microelectronic workpiece into a carrierassembly of a CMP machine, the microelectronic workpiece comprising asubstrate including an outer layer comprising germanium and selenium;delivering a process solution to a processing pad, the process solutionand processing pad comprising a removal medium, the process solutioncomprising a fluid component having a pH of at least about 8 and a solidcomponent comprising abrasive particles; removing material of the outerlayer from the workpiece by rubbing the outer layer against the removalmedium with a controlled force of about 0.1-2 psi.
 36. The method ofclaim 35 wherein the material of the outer layer is removed by rubbingwithout substantial delamination of the outer layer.
 37. The method ofclaim 35 wherein the solid component comprises about 1-30 weight percentof the process solution delivered to the processing pad.
 38. The methodof claim 35 wherein the abrasive particles of the process solutiondelivered to the processing pad have a mean particle size of about 30-50nm.
 39. The method of claim 38 wherein the solid component comprisesabout 1-30 weight percent of the process solution.
 40. The method ofclaim 35 wherein the abrasive particles comprise silica or ceriaparticles.
 41. The method of claim 35 wherein the microelectronicworkpiece includes an intermediate layer disposed between the substrateand the outer layer, outer layer being removed to expose theintermediate layer.
 42. The method of claim 41 wherein the intermediatelayer comprises a material having a removal rate slower than a removalrate of the outer layer, the intermediate layer acting as a polish stop.43. The method of claim 35 wherein the outer layer includes up to 10atomic percent silver, and the abrasive particles, the controlled forceand a polishing linear velocity are selected to remove the material ofthe outer layer without substantial agglomeration of silver on apolished surface of the outer layer.
 44. A system for controlled removalof material from a microelectronic workpiece, comprising: a carrierassembly including an actuator; a removal medium comprising a processsolution and a processing pad, the removal medium including an abrasivecomprising abrasive particles having a mean particle size of about30-100 nm and a Vickers hardness number of less than about 1500, theprocess solution comprising a fluid component having a pH of about8-11.5; a workpiece loaded into the carrier assembly, the workpiecehaving an outer layer comprising germanium and selenium which isoriented toward the removal medium; and a controller operatively coupledto the actuator, the controller controlling the actuator to control adown force of the outer layer against the polishing medium to a range ofabout 0.1-2 psi.
 45. The system of claim 44 wherein the abrasiveparticles are fixed to the processing pad.
 46. The system of claim 44wherein the processing pad is a rotary pad.
 47. The polishing system ofclaim 44 wherein the processing pad is a web-format pad.
 48. The systemof claim 44 further comprising a process solution supply containing avolume of the process solution and adapted to deliver the processsolution to the processing pad, the abrasive of the removal medium beingdelivered to the processing pad as a solid component of the processsolution, the solid component comprising about 1-30 weight percent ofthe process solution.
 49. The system of claim 44 wherein the abrasivehas a mean particle size of about 30-50 nm.
 50. The system of claim 44wherein the abrasive particles comprise silica or ceria particles. 51.The system of claim 50 wherein the abrasive particles comprise silicaand ceria particles.
 52. The system of claim 44 wherein the fluidcomponent of the process solution comprises at least one of potassiumhydroxide and tetramethyl ammonium hydroxide.
 53. The system of claim 44wherein the workpiece includes a substrate and an intermediate layerbetween the substrate and the outer layer, the intermediate layercomprising a material having a hardness greater than a hardness of theouter layer.
 54. The system of claim 44 wherein the workpiece includes asubstrate and an intermediate layer between the substrate and the outerlayer, the intermediate layer comprising a material having a removalrate slower than a removal rate of the outer layer at the same downforce in contact with the removal medium.
 55. A system for controlledremoval of material from a microelectronic workpiece, comprising: acarrier assembly including an actuator; a removal medium comprising aprocess solution and a processing pad, the removal medium including anabrasive comprising abrasive particles having a mean particle size of nogreater than about 100 nm, the process solution comprising a fluidcomponent having a pH greater than 7; a workpiece loaded into thecarrier assembly, the workpiece having a substrate and an outer layeroriented toward the removal medium, the outer layer comprising(GexSey)aAgb, wherein x is about 20-80, y is about 20-80, a is about90-100, and b is about 0-10; and a controller operatively coupled to theactuator, the controller controlling the actuator to press the outerlayer against the polishing medium with a controlled down force selectedto reduce delamination of the outer layer from.
 56. The system of claim55 wherein the fluid component of the process solution has a pH of atleast about
 8. 57. The system of claim 55 wherein the fluid component ofthe process solution has a pH no greater than about 11.5.
 58. The systemof claim 55 wherein the controlled force is no greater than 2 psi.
 59. Asystem, comprising: a carrier assembly including an actuator, thecarrier assembly being adapted to hold a workpiece with an outer layerfacing downwardly; a removal medium comprising a process solution and aprocessing pad, the removal medium including an abrasive comprisingabrasive particles having a mean particle size of about 30-100 nm and aVickers hardness number of less than about 1500, the process solutioncomprising a fluid component having a pH of about 8-11.5; and acontroller operatively coupled to the actuator, the controllercontrolling the actuator to control a down force of the outer layeragainst the polishing medium to a range of about 0.1-2 psi.